At this level of investigation, Problem Identification will retain the same primary features of
Tier 1.

Tier 2 Problem Identification should summarise the state of information regarding
the site, contaminants, potential receptors, pathways, and effects based on the
information obtained previously. At this point, the conceptual model developed during
Tier 1 should be modified and refined to take into account the Tier 1 information
showing aspects that are not likely to be significant (and are therefore excluded from
further investigation) and those that are potentially significant.

Tier 2 Problem Identification is likely to include objectives for
the following:

identification of contaminants of concern including the
chemical properties of contaminants exceeding the benchmark criteria (as determined in
Tier 1 RA),

determination of the degree and extent of site contamination,

evaluation of the parameters affecting toxicity
(e.g. pH, hardness) and exposure, and

development of modified human health or ecotoxicological criteria.

At this point in the process, additional site investigations may be required to
further define the extent and degree of contamination, the characteristics of potentially
affected receptors and habitats, and refine understanding of the site conditions affecting
contaminant toxicity and mobility. The focus of site
investigations will depend on the objectives for the Tier 2 RA, and on the quality and
breadth of information obtained during the previous site investigations.

Tier 3 Problem Identification should summarise the state of information regarding
the site, contaminants, potential receptors, pathways, and effects based on the
information obtained previously. At this point, the conceptual model modified and
refined during Tier 2 should be further refined to take into account the
additional information collected.

The Tier 3 Problem Identification is likely to include a definition of objectives for
the following:

identification of contaminants of concern including the properties of each chemical form
and mixtures for contaminants exceeding modified ecotoxicological criteria (as determined in
Tier 2 RA),

modelling predictions about current and future risks to site-specific ecological values
or human receptors,

evaluation of the refined parameters affecting toxicity and exposure assessments,

determination of the modified criteria.

At this point in the process, further site investigations may need to be undertaken to
fully define the characteristics of potentially affected populations for species of
concern, and refine understanding of the site conditions affecting contaminant
toxicity and mobility. Other information that could be required may include: